Method and system for emitting offset illumination for reduced stray light

ABSTRACT

A method for example of irradiating a light-curable material, may comprise irradiating light about a first axis from an array of light-emitting elements towards a light-curable surface, directing the irradiated light through an optical element interposed between the array of light-emitting elements and the light-curable surface, wherein a central axis of the optical element is offset from the first axis, and deflecting the irradiated light directed through the optical element asymmetrically away from the first axis towards the light-curable surface.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/558,583, entitled “METHOD AND SYSTEM FOR EMITTING OFFSETILLUMINATION FOR REDUCED STRAY LIGHT,” and filed on Dec. 2, 2014, whichclaims priority to U.S. Provisional Application No. 61/912,477, entitled“METHOD AND SYSTEM FOR EMITTING OFFSET ILLUMINATION FOR REDUCED STRAYLIGHT,” and filed on Dec. 5, 2013, the entire contents of each of whichare hereby incorporated by reference for all purposes.

BACKGROUND AND SUMMARY

Conventional printing and curing systems and methods may compriseapplying and curing light-curable materials such as UV-curable ink, andthe like to a substrate such as a polymer film or paper. In particular,a light-curable material, such as ink, may first be applied to thesubstrate via a printer head. Subsequently, the light-curable materialmay be cured onto the substrate using a light source. In conventionalsystems, the printer head is positioned adjacent to the light source sothat the light-curable material may be expediently cured followingapplication of the light-curable material onto the substrate via theprinter head. Accordingly, a portion of the light emitted from the lightsource may be reflected back onto the printer head after striking thetarget substrate, causing curing of the light-curable material (e.g.,light-curable ink) at the printer head surface before it can be appliedto the target substrate, and leading to accelerated printer headdegradation. A conventional approach to alleviating curing of ink at theprinter head includes positioning the printer head (and light source) atan increased distance from the substrate so that reflected light fromthe target substrate incident at the printer head is attenuated. Anotherconventional approach includes using baffles positioned to block theportion of emitted light from the light source that can potentially bereflected onto the printer head, and baffles positioned to blockreflected light before it can reach the print head.

The inventors herein have recognized potential issues with the aboveapproaches. Namely, increasing the distance of the printer head from thesubstrate can attenuate the irradiance of light at the substratesurface, resulting in longer curing times and lower system efficiency.Furthermore, the use of baffles increases the cost and complexity of theapparatus setup, and the presence of baffles in the vicinity of theprinter head and light source can interfere with printing reliabilityand light emission at the light-curable surface.

One approach that at least partially addresses the above issues includesa method of irradiating a light-curable material, comprising irradiatinglight about a first axis from an array of light-emitting elementstowards a light-curable surface, directing the irradiated light throughan optical element interposed between the array of light-emittingelements and the light-curable surface, wherein a central axis of theoptical element is offset from the first axis, and deflecting theirradiated light directed through the optical element asymmetricallyaway from the first axis towards the light-curable surface.

In another embodiment, a printing and curing system may comprise alighting module, including an array of light-emitting elements, couplingoptics, and a controller with executable instructions to position thecoupling optics over the array, wherein a central axis of the couplingoptics is offset from the first axis of the array of light-emittingelements, irradiate light about a first axis from the array oflight-emitting elements towards a light-curable surface, direct theirradiated light through the coupling optics, and deflect the irradiatedlight directed through the coupling optics asymmetrically away from thefirst axis towards the light-curable surface.

In a further embodiment, a lighting module may comprise an array oflight-emitting elements. The array emitting light symmetrically about afirst axis towards a light-curable surface, and an optical element,interposed between the array and the light-curable surface, wherein acentral axis of the optical element is offset from the first axis toasymmetrically direct the emitted light from the array of light-emittingelements away from the first axis towards the light-curable substrate.

In this manner, the technical result of deflecting emitted light fromthe light source away from a printer head in a printing and curingsystem to reduce reflection of light from a target substrate to theprinter head, to reduce curing of light-curable material at the printerhead, and to reduce printer head degradation may be achieved.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a near-Lambertian emission pattern.

FIG. 2 is a schematic of an example of a regularly spaced linear arrayof light-emitting elements.

FIG. 3 is a schematic illustrating an irradiance pattern for theregularly spaced linear array of light-emitting elements of FIG. 2.

FIGS. 4A and 4B illustrate example light sources and an adjacent printerhead.

FIGS. 5A and 5B are side cross-sectional views of a light emissionpattern from a light source.

FIGS. 6A and 6B are side cross-sectional views of a light emissionpattern from a light source.

FIGS. 7A and 7B are side cross-sectional views of a light emissionspectrum from a light source.

FIG. 8 is a schematic illustrating an example of a lighting system.

FIG. 9 illustrates an example optical element module.

FIG. 10 is a frontal perspective view of an example light source.

FIGS. 11A and 11B illustrate a frontal perspective view and across-sectional view of an example optical element module.

FIG. 12 illustrates a schematic showing a central axis of a lens.

FIG. 13 is an example flow chart for a method of irradiating alight-curable coating.

FIGS. 14A and 14C are perspective views of example cylindrical Fresnellenses.

FIGS. 14B and 14D are cross-sections of the example cylindrical Fresnellenses of 14A and 14C, respectively.

FIG. 15 is a partial side perspective view of an example light sourcewith a cylindrical Fresnel lens.

DETAILED DESCRIPTION

The present description relates to printer and coating system and amethod of using therefor. In conventional printing and curing systemsusing light-curable ink, light emitted from the light source may bereflected back into the printer head after striking the targetsubstrate, leading to curing of the ink before it can be applied to thetarget substrate, and printer head degradation. The inventors herein usea lens to offset or deflect the emitted light rays from a light sourcethereby preventing the reflected light rays from entering the printhead. This configuration has the advantage of preventing the material tobe cured before it reaches the target substrate.

FIG. 1 illustrates an example of a near-Lambertian emission pattern foran LED light-emitting element. FIG. 2 shows a schematic depicting anexample of a linear array of light-emitting elements arranged in aregularly spaced manner, and FIG. 3 illustrates an example of anirradiance pattern for the regularly spaced linear array oflight-emitting elements shown in FIG. 2. FIGS. 4A and 4B illustrate anexample light source and printer head, with no optics and with an offsetcylindrical lens, respectively. FIG. 5 shows a schematic of a sidecross-sectional view of light emission from a light source. FIG. 6 showsa schematic of a side cross-sectional view of light emission from alight source including an offset cylindrical lens. FIG. 7 shows a sideview of light emission (with offset rod lens). FIG. 8 is a schematic ofan example configuration for a light source. FIG. 9 illustrates anexample optical element module, and FIG. 10 is a frontal perspectiveview of an example light source. An example of an optical element moduleis depicted in FIG. 11A and 11B. FIG. 12 illustrates a central axis ofan optical element. FIG. 13 is an example flow chart for a method ofirradiating a light-curable coating. Examples of multi-groove andsingle-groove cylindrical Fresnel lenses are depicted in FIGS. 14A, 14B,14C, and 14D. FIG. 15 illustrates an example of a light sourcecomprising a single-groove cylindrical Fresnel lens.

Turning now to FIG. 1, it illustrates an emission pattern 100 for anear-Lambertian light source such as an LED type light-emitting element.The emission pattern illustrates that the angular spread of lightoriginating from the near-Lambertian light source is broad andsymmetrically dispersed about a main light-emitting axis 104 coincidentwith a 0 scan angle. Furthermore, a radiant intensity profile 110 isvariable as the emission angle from the light source is varied from −90°to +90°. Accordingly, a surface illuminated by a near-Lambertian lightsource may not be uniformly irradiated with light.

FIG. 2 illustrates a simple schematic of an example of a high aspectratio array 200 of light-emitting elements. In one example, thelight-emitting elements may comprise Lambertian light-emitting elements.As shown in FIG. 2, high aspect ratio array 200 comprises a regularlyspaced 36 mm linear array of ten light-emitting elements 220. Regularlyspaced implies that a spacing 240 between each light-emitting elementmay be the same. The light-emitting elements may be mounted on asubstrate 210, for example a printed circuit board (PCB). In addition tolinear arrays of light-emitting elements, high aspect ratio arrays mayalso include two-dimensional arrays of light-emitting elements. Twodimensional high aspect ratio arrays may comprise a first number oflight-emitting elements in a first dimension and a second number oflight-emitting elements in a second dimension, wherein the first numberis at least much larger than the second number. For example, a 2×8two-dimensional array of light-emitting elements may be considered ahigh aspect ratio array.

FIG. 3 illustrates a plot 300 of an irradiance pattern at a fixed planelocated 6 mm away from the regularly spaced linear array of LEDs in FIG.2. The irradiance pattern of plot 300 may be generated using an opticalsimulation program such as Zemax. Curves 310, 320, 330, 340, 350, and360 approximate lines of constant irradiance at a surface 6 mm away fromthe light source oriented perpendicular to the 90° emission angle of1.80, 1.65, 1.30, 0.90, 0.40, and 0.20 W/cm² respectively. FIG. 3illustrates the angular spread of light emitted from the linearregular-spaced array in a widthwise axis and a lengthwise axis.Irradiance from the regularly spaced array varies across the twodimensional pattern decreasing in intensity from the center of thepattern towards the periphery. As shown in the irradiance pattern ofFIG. 3, the distribution of light is broadly dispersed about a mainlight-emitting axis 304.

Turning now to FIG. 10, it illustrates a frontal perspective view of anexample light source 1000. The light source comprises a housing 1010containing a linear array of light-emitting elements, a window and afront cover 1016 at the front plane of the housing 1010, sidewalls 1018,and fasteners 1030. As illustrated, the light source 1000 may have ahousing 1010 shaped as a square or rounded rectangular box. Otherhousing shapes where sidewalls extend backwards perpendicularly from thefront plane of the housing and where light sources may be positionedflush when side by side may be used.

Turning to FIG. 4A, it illustrates a schematic of a printer and coatingsystem 400, including housing 1010 of a light source 1000, such as lightsource 1000 described above in FIG. 10. Printer and coating system 400may include a printer 410. Printer 410 may comprise a printer head 430mounted and/or positioned wherein a bottom surface 450 is flush with thebottom surface (e.g., front cover 1016) of the housing 1010 of the lightsource 1000. Bottom surface 450 may also be referred to as the printerhead surface, as the printing ink is jetted out from the printer headvia bottom surface 450. As shown in FIG. 10, light is emitted from lightsource 1000 via front cover 1016. Accordingly, both the printing ink andthe light are emitted via a common plane aligned with both the bottomsurface 450 of the printer head 430 and the front cover 1016 of lightsource 1000. As shown in FIG. 4A, light rays 420 may be symmetricallyemitted by the light source 1000 about a main light-emitting axis 470and reflected at target substrate 440. As illustrated in FIG. 4A, someof the reflected light rays from the target substrate 440 can bereflected from the substrate back into the printer head 430, causingprinter head misfiring or printer head jetting problems due to curing ofthe ink at the printer head nozzles. Printer head may further comprisesensors 436 distributed across the printer head for measuring lightirradiated onto the printer head surface. In this way, light reflectedfrom the target substrate 440 onto the printer head may be measured andinput to a controller 1414.

Turning to FIG. 4B, it illustrates a schematic of a modified printingand curing system 401, further comprising a cylindrical lens 660positioned inside the housing 1010 of the light source 1000. Thecylindrical lens 660 is positioned such that a bottom light-emittingsurface of the cylindrical lens 660 is flush or slightly recessed fromthe front cover 1016 such that the front cover 1016 remains flush withthe bottom surface 450 of the printer head 430. As illustrated in FIG.4B, the cylindrical lens 660 may be aligned off-axis from the lightsource, whereby light rays emitted from its light-emitting surface andfrom front cover 1016 are redirected about a tilted axis of propagation480 (e.g., a light emitting-axis about which the emitted light rays arecentrally dispersed). The tilted axis of propagation 480 is tilted orangled away from the main light emitting axis 470 of the light source.The degree of tilt (e.g., angular deflection) of the tilted axis ofpropagation 480 relative to the main light-emitting axis 470 may bedependent on the magnitude of the offset (e.g. off-axis alignment) ofthe cylindrical lens 660 relative to the main light-emitting axis 470 ofthe light source, as well as other factors including the shape andgeometry of the cylindrical lens. The offset of the cylindrical lens 660may be characterized by an offset of a central axis 404 of thecylindrical lens 660 by a distance 402 from the main light emitting axis470. If a central axis of a lens is aligned with a main light-emittingaxis 470 (e.g., no offset and distance 402 is zero) of the light source1000, then emitted light rays may not be deflected away from the printerhead 430.

In some examples, the central axis of the lens may pass through thephysical center of the lens. The central axis may also be aligned with alongitudinal axis of the lens, the longitudinal axis of the lens passingthrough a longitudinal center of the lens. For example, in the case of arotationally symmetric lens, the central axis may be perpendicular tothe apex (positive lens) or valley (negative lens), typically in thephysical center of the lens. In the case of a non-rotationally symmetriclens, the central axis may be the intersection of two planes defined bythe apex or valley of one axis (e.g., short axis) and the apex or valleyof the second axis (e.g., longitudinal axis). As shown in FIG. 12, ifone axis does not have power (e.g., a cylindrical lens), then thecentral axis may be given by the plane perpendicular to the apex orvalley of the powered axis, and the physical center of the non-poweredaxis.

For example, increasing the degree of offset of the cylindrical lens 660from the main light-emitting axis 470 may increase the degree Φ of tiltof the tilted axis of propagation 480. Accordingly, the emitted lightmay thereby be deflected to one side of the main light-emitting axis470, at an angle determined by the amount of offset. Deflecting theemitted or irradiated light rays may comprise one or more of refracting,reflecting, diffracting, collimating, and focusing the light rays.

As shown in FIG. 4B, reflection of the tilted and off-set reflectedlight rays 460 into the printer head 430 may be reduced. As such, curingof light curable material at the surface of the printer head may bemitigated and printer head degradation may be reduced. Further still, adistance 490 between the printer head and the target substrate 440 maybe reduced, thereby increasing curing rates and increasing theefficiency of the printer and coating system relative to conventionalsystems and methods.

Turning now to FIG. 9, it illustrates a picture of an optical elementmodule 900 for an optical element 910, the optical element 910comprising of central axis 916. The perimeter of the optical elementmodule 900 is delineated by an outer edge 902 of the optical elementmodule 900 that is raised relative to a recessed lens region 906 andrelative to a recessed mounting region 912. Optical element 910 can beof various geometrical configurations (e.g., rod, Fresnel, cylindricaland the like) and the recessed shape of the recessed lens region 906 mayhelp to accommodate optical elements of various geometries. Recessedalignment region 902 may aid in aligning the optical element module 900to a light source. For example, the optical elements can be secured inposition by fasteners which may be positioned in the fastener holders904. The recessed alignment region may further comprise a plurality ofadjustment ridges 908. Aligning a mounting edge of the optical element910 to one or more of the adjustment ridges 908 may aid in positioningthe optical element 910 to achieve a particular offset distance 402between the central axis 916 of the optical element 910 and the mainlight-emitting axis of the emitted light rays as described above withreference to FIG. 4B. Furthermore, the optical element module 900 mayinclude one or more spacing supports 914, located near the outer edge902 of the optical element module 900. The spacing supports 914 mayprovide additional support to secure the optical element 910 in theoptical element module 900.

FIGS. 5A and 5B are illustrations showing cross-sectional views along alongitudinal axis of a high aspect ratio array of light-emittingelements. Similar to high aspect ratio array 200 of FIG. 4A describedabove in FIG. 2, the light-emitting elements may emit light having anear Lambertian profile about a main emitting axis 550. Printing axis560 parallel to the main emitting axis 550 shows an example pathtravelled by printing ink after being dispensed from the printer head tothe substrate, wherein the printer head may be positioned adjacent tolight source 1000, as shown in FIG. 4A. Thus, in accordance with FIGS.4A and 4B, a printer head and printer head surface dispensing ink may bepositioned along printing axis 560 and at a position coplanar with lightemitting surface of front cover 1016.

FIG. 5A further illustrates a shaded light intensity spectrum 502 oflight emitted from light source 1000. As shown in FIG. 5A, the lightintensity is most concentrated a short distance from light source 1000,and disperses quickly at distances further from light source 1000. FIG.5B is an illustration superimposing the light intensity spectrum 502 ofFIG. 5A as linear contours 520, 530, and 540 in schematic form.

As shown in FIG. 5B, light rays 570, extend symmetrically about bothsides of main light-emitting axis 550, including extending beyondprinting axis 560. A situation similar to FIG. 4A is represented whereinthe light rays travelling beyond printing axis 560 may be reflected fromthe substrate to the printer head.

FIGS. 6A and 6B, show side cross-sectional views of light emissionspectrum from a light source with offset cylindrical lens 660. FIG. 6Afurther illustrates a shaded light intensity spectrum 602 of lightemitted from light source 1000. FIG. 6B is an illustration superimposingthe light intensity spectrum 602 of FIG. 6A as linear contours 610, 620,and 630 in schematic form. The linear contours 610, 620, and 630illustrated in FIG. 6B represents zones of equal light intensity. Theemitted light rays 680 as shown in FIG. 6B illustrates the direction inwhich the light rays coming from the light source 1000 may be directedby the offset cylindrical lens 660. Unlike FIG. 5B, the emitted lightrays 680 in FIG. 6B, do not extend symmetrically about both sides of themain light emitting axis 550. As shown in FIG. 6B, due to inclusion ofthe offset cylindrical lens 660, the central axis 650 is offset from themain light emitting axis 550. This shift of the main light emitting axis550 to central axis 650, indicates deflection of the emitted light rays680 away from the printing axis 560. The cylindrical lens 660, as shownin FIG.6B, can be of various geometrical configuration.

A situation similar to FIG. 6A and 6B is represented in FIGS. 7A and 7B.FIGS. 7A and 7B show side cross-sectional views of light emissionspectrum from a light source with offset rod lens 740. FIG. 7A furtherillustrates a shaded light intensity spectrum 702 of light emitted fromlight source 1000. FIG. 7B is an illustration superimposing the lightintensity spectrum 702 of FIG. 6A as linear contours 710, 720, and 730in schematic form. The linear contours 710, 720, and 730 illustrated inFIG. 7B represent zones of equal light intensity. Unlike FIG. 5B, theemitted light rays 760 in FIG. 7B, do not extend symmetrically aboutboth sides of the main light emitting axis 550. FIG. 7B illustrates thedirection in which the light rays emitted from the light source 1000 maybe directed by the offset rod lens 740. As shown in FIG. 7B, the centralaxis 750 is offset from the main light emitting axis 550. This shift ofthe main light emitting axis 550 to central axis 750, indicatesdeflection of the emitted light rays 760 away from the printing axis560. Inclusion of the rod lens 740, allows the emitted light rays 760 tobe deflected away from the printing axis 560. Additionally, inclusion ofrods lens 740, concentrates the light rays 760 on the target substrate440. In comparison to emitted light rays 570 in FIG. 5B and emittedlight rays 680 in FIG. 6B, emitted light rays 760 in FIG. 7B may be moreconcentrated, with more focused emitted light rays deflected away fromthe main light emitting axis 550 towards the target substrate 440,described above in FIG. 4A. The increased concentration of the emittedlight rays 760 in comparison to emitted light rays 570 and emitted lightrays 680, has the potential advantage of increasing curing rate andincreasing efficiency of the printing and curing system.

Referring now to FIG. 8, it illustrates a block diagram for an exampleconfiguration of lighting system 1400. As an example, printing andcuring system may comprise lighting system 1400, wherein a printer 410including a printer head 430 may be positioned adjacent to a lightingsystem 1400. For example, FIG. 4B illustrates a printing and curingsystem wherein a printer 410 is positioned adjacent to a light source1000 (e.g., a lighting subsystem).

In one example, lighting system 1400 may comprise a light-emittingsubsystem 1412, a controller 1414, a power source 1416 and a coolingsubsystem 1418. The light-emitting subsystem 1412 may comprise aplurality of semiconductor devices 1419. The plurality of semiconductordevices 1419 may be a linear array 1420 of light-emitting elements suchas a linear array of LED devices, for example. Semiconductor devices mayprovide radiant output 1424. The radiant output 1424 may be directed toa workpiece 1426 located at a fixed plane from lighting system 1400.Furthermore, the linear array of light-emitting elements may be an edgeweighted linear array of light-emitting elements, wherein one or moremethods are employed to increase the useable length of light output atworkpiece 1426. For example, one or more of edge weighted spacing,lensing (e.g. providing coupling optics) of individual light-emittingelements, providing individual light-emitting elements of differentintensity, and supplying differential current to individual LEDs may beemployed as described above.

The radiant output 1424 may be directed to the workpiece 1426 viacoupling optics 1430. The coupling optics 1430, if used, may bevariously implemented. As an example, the coupling optics may includeone or more layers, materials or other structures interposed between thesemiconductor devices 1419 and window 1464, and providing radiant output1424 to surfaces of the workpiece 1426. As an example, the couplingoptics 1430 may include a micro-lens array to enhance collection,condensing, collimation or otherwise the quality or effective quantityof the radiant output 1424. As another example, the coupling optics 1430may include a micro-reflector array. In employing such a micro-reflectorarray, each semiconductor device providing radiant output 1424 may bedisposed in a respective micro-reflector, on a one-to-one basis. Asanother example, a linear array of semiconductor devices 1420 providingradiant output 24 and 25 may be disposed in macro-reflectors, on amany-to-one basis. In this manner, coupling optics 1430 may include bothmicro-reflector arrays, wherein each semiconductor device is disposed ona one-to-one basis in a respective micro-reflector, and macro-reflectorswherein the quantity and/or quality of the radiant output 1424 from thesemiconductor devices is further enhanced by macro-reflectors.

Each of the layers, materials or other structure of coupling optics 1430may have a selected index of refraction. By properly selecting eachindex of refraction, reflection at interfaces between layers, materialsand other structures in the path of the radiant output 1424 may beselectively controlled. As an example, by controlling differences insuch indexes of refraction at a selected interface, for example window1464, disposed between the semiconductor devices to the workpiece 1426,reflection at that interface may be reduced or increased so as toenhance the transmission of radiant output at that interface forultimate delivery to the workpiece 1426. For example, the couplingoptics may include a dichroic reflector where certain wavelengths ofincident light are absorbed, while others are reflected and focused tothe surface of workpiece 1426.

The coupling optics 1430 may be employed for various purposes. Examplepurposes include, among others, to protect the semiconductor devices1419, to retain cooling fluid associated with the cooling subsystem1418, to collect, condense and/or collimate the radiant output 1424, orfor other purposes, alone or in combination. As a further example, thelighting system 1400 may employ coupling optics 1430 so as to enhancethe effective quality, uniformity, or quantity of the radiant output1424, particularly as delivered to the workpiece 1426.

As a further example, coupling optics 1430 may comprise a cylindricalFresnel lens such as a linear cylindrical Fresnel lens for collimatingand/or focusing the light emitted from the linear array 1420 ofsemiconductor devices 1419. In particular, a cylindrical Fresnel lensmay be aligned with the linear array 1420, wherein emitted lighttherefrom is emitted through the cylindrical Fresnel lens and whereinthe cylindrical Fresnel lens reduces the angular spread of light in awidthwise axis of the linear array, the linear array spanning a lenslength. In some examples, a cylindrical Fresnel lens may be used inplace of a window, such as window 1020, as shown in FIG. 15. Thecylindrical Fresnel lens may be a single-groove lens or a multiplegroove lens to further reduce the angular spread of emitted light in awidthwise axis as compared to a single cylindrical Fresnel lens.

Selected of the plurality of semiconductor devices 1419 may be coupledto the controller 1414 via coupling electronics 1422, so as to providedata to the controller 1414. As described further below, the controller1414 may also be implemented to control such data-providingsemiconductor devices, e.g., via the coupling electronics 1422. Thecontroller 1414 may be connected to, and may be implemented to control,the power source 1416, and the cooling subsystem 1418. For example, thecontroller may supply a larger drive current to light-emitting elementsdistributed in the middle portion of linear array 1420 and a smallerdrive current to light-emitting elements distributed in the end portionsof linear array 1420 in order to increase the useable length of lightirradiated at workpiece 1426. Moreover, the controller 1414 may receivedata from power source 1416 and cooling subsystem 1418. In one example,the irradiance at one or more locations at the workpiece 1426 surfacemay be detected by sensors and transmitted to controller 1414 in afeedback control scheme. In a further example, controller 1414 maycommunicate with a controller of another lighting system (not shown inFIG. 8) to coordinate control of both lighting systems. For example,controller 1414 of multiple lighting systems may operate in amaster-slave cascading control algorithm, where the set point of one ofthe controllers is set by the output of the other controller. Othercontrol strategies for operation of lighting system 10 in conjunctionwith another lighting system may also be used. As another example,controller 1414 for multiple lighting systems arranged side by side maycontrol lighting systems in an identical manner for increasinguniformity of irradiated light across multiple lighting systems.

In addition to the power source 1416, cooling subsystem 1418, andlight-emitting subsystem 1412, the controller 1414 may also be connectedto, and implemented to control internal element 1432, and externalelement 1434. Element 1432, as shown, may be internal to the lightingsystem 1410, while element 1434, as shown, may be external to thelighting system 1410, but may be associated with the workpiece 1426(e.g., handling, cooling or other external equipment) or may beotherwise related to a photoreaction (e.g. curing) that lighting system1410 supports.

The data received by the controller 1414 from one or more of the powersource 1416, the cooling subsystem 1418, the light-emitting subsystem1412, and/or elements 1432 and 1434, may be of various types. As anexample, the data may be representative of one or more characteristicsassociated with coupled semiconductor devices 1419. As another example,the data may be representative of one or more characteristics associatedwith the respective light-emitting subsystem 1412, power source 1416,cooling subsystem 1418, internal element 1432, and external element 1434providing the data. As still another example, the data may berepresentative of one or more characteristics associated with theworkpiece 1426 (e.g., representative of the radiant output energy orspectral component(s) directed to the workpiece). Moreover, the data maybe representative of some combination of these characteristics.

The controller 1414, in receipt of any such data, may be implemented torespond to that data. For example, responsive to such data from any suchcomponent, the controller 1414 may be implemented to control one or moreof the power source 1416, cooling subsystem 1418, light-emittingsubsystem 1412 (including one or more such coupled semiconductordevices), and/or the elements 32 and 34. As an example, responsive todata from the light-emitting subsystem indicating that the light energyis insufficient at one or more points associated with the workpiece, thecontroller 1414 may be implemented to either (a) increase the powersource's supply of power to one or more of the semiconductor devices,(b) increase cooling of the light-emitting subsystem via the coolingsubsystem 1418 (e.g., certain light-emitting devices, if cooled, providegreater radiant output), (c) increase the time during which the power issupplied to such devices, or (d) a combination of the above.

In the example where a printing and curing system comprises lightingsystem 1400, controller 1414 may also receive input from light sensors436 at a printer head. For example, in response to a measured intensityof light reflected from workpiece 1426 onto the printer head, controller1414 may adjust a transverse offset of the optical element (e.g.,coupling optics 1430 of lighting system 1400) in order to reduce theintensity of light reflected from workpiece 1426 onto the printer head.

Individual semiconductor devices 1419 (e.g., LED devices) of thelight-emitting subsystem 1412 may be controlled independently bycontroller 1414. For example, controller 1414 may control a first groupof one or more individual LED devices to emit light of a firstintensity, wavelength, and the like, while controlling a second group ofone or more individual LED devices to emit light of a differentintensity, wavelength, and the like. The first group of one or moreindividual LED devices may be within the same linear array 1420 ofsemiconductor devices, or may be from more than one linear array ofsemiconductor devices 1420 from multiple lighting systems 1400. Lineararray 1420 of semiconductor device may also be controlled independentlyby controller 1414 from other linear arrays of semiconductor devices inother lighting systems. For example, the semiconductor devices of afirst linear array may be controlled to emit light of a first intensity,wavelength, and the like, while those of a second linear array inanother lighting system may be controlled to emit light of a secondintensity, wavelength, and the like.

As a further example, under a first set of conditions (e.g. for aspecific workpiece, photoreaction, and/or set of operating conditions)controller 1414 may operate lighting system 1410 to implement a firstcontrol strategy, whereas under a second set of conditions (e.g. for aspecific workpiece, photoreaction, and/or set of operating conditions)controller 1414 may operate lighting system 1410 to implement a secondcontrol strategy. As described above, the first control strategy mayinclude operating a first group of one or more individual semiconductordevices (e.g., LED devices) to emit light of a first intensity,wavelength, and the like, while the second control strategy may includeoperating a second group of one or more individual LED devices to emitlight of a second intensity, wavelength, and the like. The first groupof LED devices may be the same group of LED devices as the second group,and may span one or more arrays of LED devices, or may be a differentgroup of LED devices from the second group, but the different group ofLED devices may include a subset of one or more LED devices from thesecond group.

The cooling subsystem 1418 may be implemented to manage the thermalbehavior of the light-emitting subsystem 1412. For example, the coolingsubsystem 1418 may provide for cooling of light-emitting subsystem 1412,and more specifically, the semiconductor devices 1419. The coolingsubsystem 1418 may also be implemented to cool the workpiece 1426 and/orthe space between the workpiece 1426 and the lighting system 1410 (e.g.,the light-emitting subsystem 1412). For example, cooling subsystem 1418may comprise an air or other fluid (e.g., water) cooling system. Coolingsubsystem 1418 may also include cooling elements such as cooling finsattached to the semiconductor devices 1419, or linear array 1420thereof, or to the coupling optics 1430. For example, cooling subsystemmay include blowing cooling air over the coupling optics 1430, whereinthe coupling optics 1430 are equipped with external fins to enhance heattransfer.

The lighting system 1410 may be used for various applications. Examplesinclude, without limitation, curing applications ranging from inkprinting to the fabrication of DVDs and lithography. The applications inwhich the lighting system 1410 may be employed can have associatedoperating parameters. That is, an application may have associatedoperating parameters as follows: provision of one or more levels ofradiant power, at one or more wavelengths, applied over one or moreperiods of time. In order to properly accomplish the photoreactionassociated with the application, optical power may be delivered at ornear the workpiece 1426 at or above one or more predetermined levels ofone or a plurality of these parameters (and/or for a certain time, timesor range of times).

In order to follow an intended application's parameters, thesemiconductor devices 1419 providing radiant output 1424 may be operatedin accordance with various characteristics associated with theapplication's parameters, e.g., temperature, spectral distribution andradiant power. At the same time, the semiconductor devices 1419 may havecertain operating specifications, which may be associated with thesemiconductor devices' fabrication and, among other things, may befollowed in order to preclude destruction and/or forestall degradationof the devices. Other components of the lighting system 1410 may alsohave associated operating specifications. These specifications mayinclude ranges (e.g., maximum and minimum) for operating temperaturesand applied electrical power, among other parameter specifications.

Accordingly, the lighting system 1410 may support monitoring of theapplication's parameters. In addition, the lighting system 1410 mayprovide for monitoring of semiconductor devices 1419, including theirrespective characteristics and specifications. Moreover, the lightingsystem 1410 may also provide for monitoring of selected other componentsof the lighting system 1410, including its characteristics andspecifications.

Providing such monitoring may enable verification of the system's properoperation so that operation of lighting system 1410 may be reliablyevaluated. For example, lighting system 1410 may be operating improperlywith respect to one or more of the application's parameters (e.g.temperature, spectral distribution, radiant power, and the like), anycomponent's characteristics associated with such parameters and/or anycomponent's respective operating specifications. The provision ofmonitoring may be responsive and carried out in accordance with the datareceived by the controller 1414 from one or more of the system'scomponents.

Monitoring may also support control of the system's operation. Forexample, a control strategy may be implemented via the controller 1414,the controller 1414 receiving and being responsive to data from one ormore system components. This control strategy, as described above, maybe implemented directly (e.g., by controlling a component throughcontrol signals directed to the component, based on data respecting thatcomponents operation) or indirectly (e.g., by controlling a component'soperation through control signals directed to adjust operation of othercomponents). As an example, a semiconductor device's radiant output maybe adjusted indirectly through control signals directed to the powersource 1416 that adjust power applied to the light-emitting subsystem1412 and/or through control signals directed to the cooling subsystem1418 that adjust cooling applied to the light-emitting subsystem 1412.

Control strategies may be employed to enable and/or enhance the system'sproper operation and/or performance of the application. In a morespecific example, control may also be employed to enable and/or enhancebalance between the linear array's radiant output and its operatingtemperature, so as, e.g., to preclude heating the semiconductor devices1419 beyond their specifications while also directing sufficient radiantenergy to the workpiece 1426, for example, to carry out a photoreactionof the application. Furthermore, in some examples, a controller may beused to automatically adjust the offset position of a lens relative to amain light emitting axis of a light source in order to adjust theangular deflection of light emitted from a light source 1000 towards atarget substrate 440. Accordingly, a printing and curing system may beautomatically adjusted to various curing conditions and targetsubstrates in a continuous manner without having to manually adjust theprinting and curing system.

In some applications, high radiant power may be delivered to theworkpiece 1426, and the workpiece 1426 may comprise a light-curablematerial, including a substrate with a light-curable material printedthereon. Accordingly, the light-emitting subsystem 1412 may beimplemented using a linear array of light-emitting semiconductor devices1420. For example, the light-emitting subsystem 1412 may be implementedusing a high-density, light-emitting diode (LED) array. Although LEDarrays may be used and are described in detail herein, it is understoodthat the semiconductor devices 1419, and linear arrays 1420 thereof, maybe implemented using other light-emitting technologies without departingfrom the principles of the invention; examples of other light-emittingtechnologies include, without limitation, organic LEDs, laser diodes,other semiconductor lasers.

In this manner, a printing and curing system may comprise a lightingmodule, including an array of light-emitting elements, coupling optics,and a controller with executable instructions to position the couplingoptics over the array, wherein a central axis of the light-emittingelement is offset from a first axis of the array of light-emittingelements, irradiate light about a first axis from the array oflight-emitting elements towards a light-curable surface, direct theirradiated light through the coupling optics, and deflect the irradiatedlight directed through the coupling optics asymmetrically away from thefirst axis towards the light-curable surface. The coupling optics maycomprise a reflector, and/or a cylindrical lens, wherein the cylindricallens comprises a Fresnel lens, and/or a rod lens.

Deflecting the irradiated light directed through the optical elementasymmetrically away from the first axis may comprise deflecting theirradiated light about a second axis, wherein the second axis is angledat a deflecting angle to the first axis. Furthermore, the printing andcuring system may comprise executable instructions to increase thedeflecting angle by increasing an offset between the central axis andthe first axis.

Turning now to FIG. 11A, it illustrates a schematic frontal perspectiveview of an optical element module 1100 comprising an example rods lens1110, mounted in an optical element housing 1120. Fastening holes 1170in optical element housing 1120 may be used for mounting hardware suchas screws to secure a lens (e.g., rod lens 1110) to the optical elementhousing 1120, and for securing a mounting plate 1130 to optical elementhousing 1120. Mounting plate 1130 and housing region 1180 may betransparent such that light rays 1190 from a light source may betransmitted unhindered through mounting plate 1130 and through rod lens1110. The rod lens 1110 can be of various geometries and the outerdimensions of the optical element housing 1120 can be modular such thatdifferent optical element housings may be used to accommodate varioustypes of rod lenses or other lens geometries. Accordingly, mounting theoptical element module 1100 in a lighting module may automatically aligna main light-emitting axis of a light source to be offset from theoptical element. In particular, as shown in FIGS. 11A and 11B, opticalelement housing 1120 may comprise unequal optical element supports 1152and 1154 extending along the length of optical element housing 1120 sothat when rod lens 1110 is mounted, a central axis 1118 of rod lens isparallel, but offset from a main light-emitting axis 1136.

The side surface 1140 of the rod lens 1110 may be positioned to be flushwith the side surface 1150 of the optical element housing 1120.Additionally, the front surface 1116 of the rod lens may be flush withor slightly protrude from the front surface of the optical elementhousing 1120. In this manner the optical element housing 1120 may notinterfere or block light emitted from the rod lens 1110. In addition,when optical element module 1100 is mounted in the lighting module, thefront surface 1116 of the rod lens may be flush with or slightlyrecessed from the front cover 1016 of the light source housing 1010,described in FIGS. 4A and 4B, such that the front cover 1016 remainsflush with the bottom surface 450 of the printer head 430. Furthermore,a central axis 1118 of the rod lens 1110 may be offset from a main lightemitting axis 1136 of the light source 1000 (not shown in FIG. 11) sothat the rod lens can deflect emitted light rays away from the printerhead and towards a target substrate 440.

FIG. 11B illustrates a cross-sectional view of optical element module1100 taken at section 11B-11B taken in a plane defined by longitudinalaxis 1162 and a transverse axis 1164. The optical element housing 1120positions the mounted optical element (e.g. rod lens 1110) apart fromthe light source in a longitudinal direction. Optical element supports1152 and 1154 are of unequal length to facilitate mounting of rod lens1110 in optical element housing 1120, wherein the rod lens 1110 istransversely offset from the main light-emitting axis 1136. The offsetmay refer to wherein a central axis 1118 is transversely offset from amain light-emitting axis 1136 by an offset 1148. Furthermore, bothmounting plate 1130 and region 1180 of the optical element housingbetween the optical element (e.g., rod lens 1110) and the light sourcemay be transparent so that light rays 1190 centered about a mainlight-emitting axis 1136 from a light source may be transmittedunhindered through mounting plate 1130, region 1180 before reaching theoptical element (e.g., rod lens 1110). As an example, region 1180 may bea hole, gap or cutout in the optical element housing 1120, similar torecessed lens region 906 of optical element module 900.

Turning now to FIG. 13, it illustrates an example flow chart of a method1300 of irradiating a light-curable material. Method 1300 begins at 1310where light may be irradiated about a first axis, for example a mainlight-emitting axis of a light source, towards a light-curable surface.The light source may be a high aspect ratio array of light-emittingelements such as a linear array of LEDs. In another example, the lightsource may be a Lambertian or near-Lambertian light source, wherein theirradiated light from the light source is emitted symmetrically about afirst axis. Furthermore, the light may be irradiated from a printing andcuring system, comprising a printer and a light source. A printer headof the printer may be adjacent to and aligned in a plane with a frontcover of the light source, wherein the plane is positioned over thelight-curable substrate. In this way, light-curable material dispensedfrom the print head onto the substrate may form a light-curable surface.The light-curable surface may be cured in an expedient manner byemitting light from the light source adjacent to the printer head andaligned in the plane therewith.

Method 1310 continues at 1320 where the irradiated light is directedthrough an offset optical element. As shown in FIG. 11B, a central axisof the optical element may be offset in a transverse direction relativeto the first axis. Furthermore, the optical element may be positionedbetween the light source and the light-curable surface. The opticalelement may be a lens such as a cylindrical lens, a rod lens, a Fresnellens, and the like. The optical element may also comprise a reflector,diffractor, refractor, or collimator whose central axis is transverselyoffset from the first axis.

Next, method 1300 continues at 1330 where the irradiated light isdeflected asymmetrically away from the first axis towards thelight-curable surface. Deflecting the irradiated light may comprise oneor more of reflecting, diffracting, refracting, and collimating theirradiated light. Because the optical element is transversely offsetfrom the first axis of the light source, the irradiated light isdeflected asymmetrically away from the first axis. In this manner, lightemitted from the light source onto the light-curable substrate may bereflected away from the printer head, thereby reducing curing oflight-curable material at the printer head.

At 1340, method 1300 continues by determining if a deflecting angle isto be increased or decreased, thereby increasing or decreasing thedeflecting angle of the deflected light from the optical element. As anexample, a deflecting angle may be increased to reduce an intensity oflight reflected from the light-curable surface onto the printer head. Inthis manner, curing of light-curable material (e.g., UV-curable ink, andthe like) at the printer head may be reduced. Conversely, a deflectingangle may be reduced if an intensity of light irradiating thelight-curable surface is to be increased, for example, to increase acuring rate. In one example, a printer head surface may comprise sensorsto measure the irradiance of light reflected from the light-curablesurface at the printer head.

At 1350, if the deflecting angle is to be adjusted, a transverse offsetof the central axis of the optical element may be adjusted relative tothe main light-emitting axis of the light source. For example, if thesensors detect a higher irradiance of light reflected from thelight-curable surface (or if curing of light-curable material at theprinter head is observed), then a transverse offset of the opticalelement from the main light-emitting axis (e.g., first axis) of thelight source may be increased. Conversely, if the sensors detect a lowerirradiance of light reflected from the light-curable surface, then atransverse offset of the optical element from the main light-emittingaxis (e.g., first axis) of the light source may be maintained, or may bereduced in order to increase curing rate. As described above, thetransverse offset may be adjusted manually by changing a mountedalignment position of the optical element in the optical element module.In another example, the transverse offset may be adjusted automaticallyby a controller.

In some examples, the optical element may be mounted in an opticalelement housing, similar to optical element housing 1120, to form anoptical element module. Furthermore, securely mounting the opticalelement module to a light source may position the optical element sothat its central axis is transversely offset from the mainlight-emitting axis of the light source. Furthermore, the opticalelement housing may comprise alignment grooves so that a mountingposition of the optical element in the optical element housing may beadjusted. In this way, a magnitude or degree of transverse offset may beadjusted by adjusting the mounting position of the optical element inthe optical element housing.

In other examples, a controller may adjust the magnitude of transverseoffset of the optical element module by actuating electromechanicalservomechanisms to which the optical element module may be mounted. Bytranslating the optical element module in a transverse directionrelative to the light source, the controller may adjust the offset ofthe optical element relative to the light source. After 1350, method1300 ends.

In this manner, a method of irradiating a light-curable material maycomprise irradiating light about a first axis from an array oflight-emitting elements towards a light-curable surface, directing theirradiated light through an optical element interposed between the arrayof light-emitting elements and the light-curable surface, wherein acentral axis of the optical element is offset from the first axis,deflecting the irradiated light directed through the optical elementasymmetrically away from the first axis towards the light-curablesurface. The central axis may be parallel to but not coincident with thefirst axis. Furthermore, the irradiated light may be directed through anoptical element comprising a cylindrical lens. Further still, deflectingthe irradiated light may comprise asymmetrically collimating theirradiated light directed through the optical element towards thelight-curable surface, asymmetrically refracting the irradiated lightdirected through the optical element towards the light-curable surface,asymmetrically diffracting the irradiated light directed through theoptical element towards the light-curable surface, and/or asymmetricallyreflecting the irradiated light directed through the optical elementtowards the light-curable surface.

Deflecting the irradiated light directed through the optical elementasymmetrically away from the first axis may comprise deflecting theirradiated light about a second axis, wherein the second axis is angledat a deflecting angle to the first axis. Furthermore, the method mayfurther comprise increasing the deflecting angle by increasing an offsetbetween the central axis and the first axis.

Turning now to FIGS. 14A and 14B, they illustrate perspective andcross-section views, respectively, of an example of a multiple-groovecylindrical Fresnel lens 1600. The multiple-groove cylindrical Fresnellens in FIGS. 14A and 14B have sixteen grooves 1620, however in otherexamples, a multiple-groove cylindrical Fresnel lens may have fewer ormore grooves. As an example, a multiple-groove cylindrical Fresnel lensmay comprise 50 grooves. As a further example, a cylindrical Fresnellens may comprise a single-groove cylindrical Fresnel lens 1602 having asingle groove 1650 (e.g., a single prism) centered around a central lensaxis 1660, as illustrated by the perspective and cross-section views ofFIGS. 14C and 14D, respectively. In general, as the number of grooves ina cylindrical Fresnel lens is increased, the thickness of the lens maydecrease. In some examples, linear cylindrical Fresnel lenses may bemanufactured from glass by a glass molding process, or opticallytransparent plastic. Glass lenses may be dimensionally more heat stableat higher heat loads or higher temperatures, such as temperatures above120° C., as compared to plastic. However, glass cylindrical Fresnellenses comprising a large number of grooves may be more difficult tomanufacture precisely, as compared to plastic cylindrical Fresnel lensesbecause it may be difficult to achieve the fine sharp edges and pointsprecisely by glass molding. For example, glass molded lenses may tend tohave rounded edges and it may be more difficult to achieve multiplegrooves of a fine pitch for lenses with large numbers of grooves.Manufacturing Fresnel lenses using plastic may allow achieving sharperprism ridges and finer prism pitch surfaces for Fresnel lenses withmultiple grooves.

In order to collimate and reduce angular spread of emitted light in awidthwise axis 1604, the one or more cylindrical Fresnel grooves may beoriented parallel to the lengthwise axis 1608 of the light source.Furthermore, the cylindrical Fresnel lens may be oriented in a groove-inorientation, wherein the cylindrical Fresnel lens grooved surface 1630faces towards the light source and the planar lens surface 1640 facesaway from the light source, or a groove-out orientation, wherein thecylindrical Fresnel lens grooved surface 1630 faces away from the lightsource and the planar lens surface 1640 faces towards from the lightsource. The groove-in and groove-out orientation of the cylindricalFresnel lens may impact the transmission efficiency of light through thecylindrical Fresnel lens. The geometry and shapes of the grooves of thecylindrical Fresnel lenses shown in FIGS. 14A, 14B, 14C, and 14D are forillustrative purposes and may not be drawn to scale. The cylindricalFresnel lens may further comprise transparent lengthwise edges 1610. Asan example, the cylindrical Fresnel lens may mount to the light sourceat the lengthwise edges 1610, or may mount in an optical element housinganalogously to the optical element housing shown in FIG. 11.Furthermore, a central axis 1632 of the Fresnel lens may be offset froma main light-emitting axis of a light source in order to deflect emittedlight from the light source away from a printer head in a printing andcuring system (similar to FIG. 4B) to reduce reflection of light from atarget substrate to the printer head, curing of light-curable materialat the printer head, and printer head degradation.

Turning now to FIG. 15, it illustrates a partial side perspective viewof another example light source 1700. Light source 1700 may be similarto above-described light source 1000, and may further comprise couplingoptics. For example, coupling optics of light source 1700 may comprise acylindrical lens, for example cylindrical Fresnel lens 1720. Similar tolight sources 1000, FIG. 15 also shows light source 1700 including frontcover 1016, fasteners 1030, housing sidewalls 1018, and the linear arrayof light-emitting elements 1090. Cylindrical Fresnel lens 1720 maycomprise a single-groove or multiple-groove cylindrical Fresnel lens(e.g., cylindrical Fresnel lenses as shown in FIGS. 14C and 14Arespectively), wherein cylindrical Fresnel lens 1720 may comprise one ormore grooves 1722 on a grooved surface 1724. Cylindrical Fresnel lens1720 may have a groove-in orientation wherein grooved surface 1724 mayface towards the light-emitting elements 1090 and planar surface 1728may face away from the light-emitting elements 1090 as shown in FIG. 15.Alternately, cylindrical Fresnel lens 1720 may have a groove-outorientation, wherein grooved surface 1724 may face away from thelight-emitting elements 1090 and a planar surface 1728 of cylindricalFresnel lens may face towards the light-emitting elements 1090. Bothplanar surface 1728 and sidewalls 1786 of cylindrical Fresnel lens aretransparent. Accordingly, a portion of light irradiated from end portionlight-emitting elements adjacent to and near lens sidewalls 1786 may beirradiated through lens sidewalls 1786. Irradiation of light throughlens sidewalls 1786 of light sources may thereby reduce non-uniformitiesin irradiated light across multiple light sources arranged adjacentlyside by side as compared to conventional light sources arranged side byside. Lens sidewalls 1786 may be flush with the sides of front cover1016 and housing sidewalls 1018 so that light sources can be placed sideby side in a flush arrangement wherein a gap between the side by sidelight sources is reduced. To this end, fasteners 1030 mounted in housingsidewalls 1018 may also be recessed from the plane of housing sidewalls1018 when fully secured. As previously described, aligning the lenssidewalls 1786 to be flush with the housing sidewalls may reduce spacingbetween and may maintain continuity of irradiated light across multiplelight sources arranged side by side. Furthermore, lens sidewalls 1786may extend perpendicularly back from the front plane. In this manner,multiple light sources may be aligned flush side by side wherein firstand last light-emitting elements in the end portions of side by sidelight sources are positioned adjacent to lens sidewalls 1786, whereinthe lens sidewalls 1786 span the length of the front plane of each lightsource housing. Positioning the first and last light-emitting elementsin the linear arrays adjacent to lens sidewalls 1786 may allow side byside light sources to irradiate light across the entire length of thelens. Positioning the first and last light-emitting elements in thelinear arrays adjacent to lens sidewalls 1786 may comprise positioningthe first and last light-emitting elements wherein there may be a smallgap (e.g., gap 1082) between the window sidewalls and the first and lastlight-emitting elements respectively.

As another example, light source 1700 may further comprise a transparentwindow (not shown) mounted in a front plane of the housing and coveringthe front face of the cylindrical Fresnel lens 1720, wherein a frontface of the window is aligned approximately flush with the front planeof the housing, and window sidewalls are aligned flush with the housingsidewalls 1018. Aligning the lens sidewalls 1786 and window sidewalls tobe flush with the housing sidewalls may reduce spacing between and maymaintain continuity of irradiated light across multiple light sourcesarranged side by side.

Furthermore a central axis 1770 of the Fresnel lens may be transverselyoffset from a main light emitting axis 1772 of light-emitting elementsof light source 1700. In this manner, light emitted from light source1700 may be deflected by the Fresnel lens away from a printer head in aprinting and curing system (similar to FIG. 4B) to reduce reflection oflight from a target substrate to the printer head, curing oflight-curable material at the printer head, and printer headdegradation.

In this manner, a lighting module may comprise an array oflight-emitting elements, the array emitting light symmetrically about afirst axis towards a light-curable surface, and an optical element,interposed between the array and the light-curable surface, wherein acentral axis of the optical element is offset from the first axis toasymmetrically direct the emitted light from the array of light-emittingelements away from the first axis towards the light-curable substrate.The lighting module may further comprise an optical element housing, theoptical element mounted in the optical element housing to form anoptical element module, and wherein upon mounting the optical elementmodule in the lighting module, the central axis is offset from the firstaxis. The optical element module may comprise a removably mountableoptical element module. Furthermore, the lighting module may furthercomprise a plurality of optical element modules, each of the pluralityof optical element modules having a different optical element mountedtherein, and wherein each of the optical element modules may beinterchangeably mounted one at a time to the lighting module, whereinthe central axis is offset from the first axis. Further still, theoptical element housing may comprise a plurality of alignment ridges908, each of the plurality of alignment ridges 908 corresponding to adifferent offset between the central axis and the first axis whenaligned with a mounting edge of the optical element. The mounting edgemay comprise a groove or alignment mark on one side face of the opticalelement.

Note that the example control and estimation routines included hereincan be used with various lighting sources and lighting systemconfigurations. The control methods and routines disclosed herein may bestored as executable instructions in non-transitory memory. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied tovarious Lambertian or near-Lambertian light sources. The subject matterof the present disclosure includes all novel and non-obviouscombinations and sub-combinations of the various systems andconfigurations, and other features, functions, and/or propertiesdisclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A method, comprising: emitting radiation from an array oflight-emitting elements symmetrically about a longitudinal axis of thearray and through an optical element toward a light-curable surface; inresponse to a first condition, comprising an irradiance intensity ofreflected radiation from the light-curable surface deviating from adesired intensity by more than a threshold deviation, adjusting atransverse offset between a central axis of the optical element and thelongitudinal axis to redirect the emitted radiation about a tilted axis,the tilted axis being tilted at an angle relative to the longitudinalaxis based on a magnitude of the transverse offset.
 2. The method ofclaim 1, wherein the first condition comprises the irradiance intensityof reflected radiation being greater than the desired intensity by morethan the threshold deviation, and adjusting the transverse offsetcomprises increasing the transverse offset between the central axis ofthe optical element and the longitudinal axis to increase the angle ofthe tilted axis.
 3. The method of claim 2, wherein the first conditioncomprises the irradiance intensity of reflected radiation being lessthan the desired intensity by more than the threshold deviation, andadjusting the transverse offset comprises decreasing the transverseoffset between the central axis of the optical element and thelongitudinal axis to decrease the angle of the tilted axis.
 4. Themethod of claim 3, further comprising positioning the optical elementsuch that the central axis is parallel to the longitudinal axis.
 5. Themethod of claim 4, further comprising positioning a printer headadjacent to the array of light-emitting elements, and dispensinglight-curable material from the printer head onto the light-curablesurface.
 6. The method of claim 5, further comprising measuring theirradiance intensity of reflected radiation at a printer head surface.7. The method of claim 6, further comprising, in response to anirradiance intensity of the emitted radiation at the light-curablesurface being less than a threshold irradiance intensity, decreasing thetransverse offset between the central axis of the optical element andthe longitudinal axis to decrease the angle of the tilted axis.
 8. Themethod of claim 7, further comprising, in response to an irradianceintensity of the emitted radiation at the light-curable surface beinggreater than a threshold irradiance intensity, increasing the transverseoffset between the central axis of the optical element and thelongitudinal axis to increase the angle of the tilted axis.
 9. A method,comprising: adjustably positioning an optical element in an opticalelement module, a position of the optical element adjustable in atransverse direction to a central axis of the optical element,detachably mounting the optical element module to a lighting modulecomprising an array of light-emitting elements emitting radiationsymmetrically about a first axis, wherein the central axis is parallelto the first axis, positioning the lighting module over aradiation-curable surface, and adjusting the position of the opticalelement to offset the central axis from the first axis, whereinradiation emitted from the light-emitting elements about the first axisand through the offset optical element is propagated asymmetrically awayfrom the first axis in a direction towards the offset on to theradiation-curable surface.
 10. The method of claim 9, furthercomprising, upon detaching the mounted optical element module from thelighting module, propagating radiation emitted from the light emittingelements to the radiation-curable surface symmetrically about the firstaxis.
 11. The method of claim 10, wherein propagating the emittedradiation asymmetrically away from the first axis includes deflectingthe emitted radiation about a deflecting axis, wherein an angle betweenthe deflecting axis and the first axis is based on a magnitude of theoffset between the central axis and the first axis.
 12. The method ofclaim 11, further comprising adjustably positioning the optical elementin the optical element module, wherein a length of the optical elementspans a length of the array of light emitting elements along the firstaxis.
 13. The method of claim 12, further comprising: positioning aprinting head adjacent to the lighting module, and dispensingradiation-curable material about a printing axis parallel to the firstaxis on to the radiation curable surface.
 14. The method of claim 13,further comprising, in response to positioning the printing headadjacent to the lighting module, adjusting the position of the opticalelement to offset the central axis from the first axis away from theprinting head.
 15. A lighting module, comprising: an array oflight-emitting elements positioned within a lighting module housing toemit radiation symmetrically about a longitudinal axis of the array, anoptical element adjustably positioned in an optical element module, theoptical element module detachably mounted to the lighting modulehousing, wherein the emitted radiation is directed through the opticalelement, a central axis of the optical element is parallel to andtransversely offset from the longitudinal axis, and upon passing throughthe optical element, the emitted radiation is deflected about a tiltedaxis of propagation away from the longitudinal axis toward the centralaxis.
 16. The lighting module of claim 15, wherein the optical elementbeing adjustably positioned in the optical element module comprises aposition of the optical element being adjustable in a directiontransverse to the central axis of the optical element.
 17. The lightingmodule of claim 16, wherein upon detaching the optical element from thelighting module housing, the emitted radiation remains symmetricallyirradiated about the longitudinal axis of the array.
 18. The lightingmodule of claim 17, wherein a length of the optical element spans alength of the array along the longitudinal axis.
 19. The lighting moduleof claim 18, wherein the optical element comprises a single contiguousoptical element.
 20. The lighting module of claim 19 wherein the arrayof light-emitting elements comprises a linear array of light-emittingelements.